SEOUL, South Korea — Kim Jong Un’s top military official - a key mentor to North Korea’s new young leader - has been removed from all posts because of illness, state media said Monday.

At least one analyst speculated that a more likely reason for Ri Yong Ho’s departure is Kim’s desire to put his own mark on the government he inherited from his father late last year.

The decision to relieve Ri of his duties was made at a Workers’ Party meeting Sunday, according to the North’s official Korean Central News Agency. It was not immediately clear who would take Ri’s place, and the North Korean media dispatch did not elaborate on Ri’s condition or future.

Ri was vice marshal of the Korean People’s Army and the military’s General Staff chief, as well as a top figure in the Workers’ Party.

He has been at Kim Jong Un’s side since the young man emerged as father Kim Jong Il’s successor in 2010, often standing between father and son at major events. That role appeared to deepen after Kim Jong Il’s death in December, helping Kim to solidify support among the military.

Kim Jong Il’s “military first” policy made the army North Korea’s most powerful institution. Ri wielded power from his position at the intersection of three crucial institutions: the Korean People’s Army, the Central Military Commission of the ruling Workers’ Party and the Standing Committee of the party’s influential Political Bureau.

Ri also oversaw an influential Kim Jong Un support group comprising officers in their 50s and 60s whom commanders consider rising stars, according to Ken Gause, a North Korea specialist at CNA, a U.S.-based research organization.

Hong Hyun-ik, an analyst at private Sejong Institute near Seoul, was skeptical about the illness claim, saying that when top North Korean officials do get sick, they typically remain in office while deputies handle their duties. There had been no previous sign that Ri was ill, he added.

Hong said the change appears aimed at replacing an appointee of Kim’s late father, Kim Jong Il, with a closer confidant.

“It can be seen as part of a general change,” Hong said, adding that he expects similar news on the dismissal of other aging, senior officials will come out in coming weeks.

Animosity on the Korean Peninsula has deepened since a North Korean rocket launch in April that the United States called a cover for a banned long-range missile test. North Korea says it was a satellite launch.

North Korea has repeatedly threatened harm to South Korea’s president and his supporters in recent months, angry over perceived insults to its leadership and recent U.S.-South Korean military drills that Pyongyang says are a prelude to an invasion.